Influence of hybrid fibers on static and dynamic behavior of RC beams

摘要

Concrete is the most frequently used building material all over the world because of its ease formability and availability. Over the last few years, utilization of fibers in concrete structures for strengthening purpose has also been increased due to its enhanced properties after cracking of the composite matrix. This research work has been focused with an objective to evaluate the behavior of reinforced concrete (RC) beams incorporated with mono and hybrid fibers under static and dynamic tests. Mechanical properties like compressive strength, split tensile strength and flexural strength were determined. From the results of mechanical properties, it has been observed that there was marginal improvement in compressive strength and significant improvement in split tensile strength and flexural strength. Later-stage RC beams with the inclusion of optimum dosage of mono and hybrid fibers have been cast and assessed its static and dynamic behaviors. Dynamic behavior of damaged and undamaged RC beams strengthened with mono steel and polypropylene (PP) fibers and also hybrid fibers (steel and PP) was investigated using the impact hammer technique. The envelopes of the frequency response function (FRF) obtained by the experimental modal analysis and the variation in dynamic property values are determined from curve fitted FRFs using modal analysis software, and the results are correlated with the damage level. The load-carrying capacity of beam with hybrid steel and PP fibers was increased compared to RC beams with mono fiber and control RC beams from static behavior results. It is observed that reduction in natural frequency values is less due to damage induced for the beams with hybrid fibers compared to that of control RC and RC beams with mono fibers. Furthermore, modeling of RC beams strengthened with mono steel and PP fibers by finite element method (FEM) has been done for the undamaged condition of the beams. Eventually, the results obtained from the FEM modeling were also compared with the experimental values, and the variation between experimental results and values obtained by FEM model is within 15%.